This invention relates to a pad wear indicator for informing the user of brake pad wear and more particularly to a pad wear indicator for informing the user of brake pad wear in response to the broken line state of an electric wire path disposed in a pad wear indicator probe wearing together with a brake pad.
A pad wear indicator comprises a pad wear indicator probe containing a U-shaped electric wire path that is broken when the probe wears together with its corresponding brake pad and includes a pad wear indicator display for detecting the broken line state of the electric wire path for displaying the wear state of the brake pad. FIGS. 10 and 11 show, respectively, a conventional pad wear indicator probe and a corresponding conventional pad wear indicator display.
To form the pad wear indicator probe 1, a copper wire 3 having barrel parts 2 that can be crimped onto electric wires formed at both ends is formed into a U-like shape, and the barrel parts 2 are crimped onto a pair of electric wires 4 whose tips are coated. The entire assembly is molded in resin. The U-shaped turn part is directed toward the brake disk side for use as a brake pad.
The pad wear indicator display 5 (FIG. 11) comprises a relay 7 having an electro-magnetic coil 6 in series with the pad wear probe 1 that is connected to a power line. An indicator lamp 9 in series with an electro-magnetic switch 8 of the relay 7 is also connected to the power line. The electro-magnetic switch 8 is turned off when the electro-magnetic coil 6 is energized.
With this construction, the copper wire 3, located within the pad wear probe 1, initially supplies power to the electro-magnetic coil of the relay 7 via the electric wire 4 and the copper wire 3 (FIG. 11). Therefore, the electro-magnetic switch 8 is turned off as shown with the broken line, and the indicator lamp 9 cannot be energized.
As a brake is used, the lining of its brake pad wears along with the pad wear probe 1. When the probe wears a predetermined amount from the tip, the turn part or bend of the copper wire 3 in the pad wear probe I wears until it is eventually cut, thus opening the circuit. Then, the energization path to the electro-magnetic coil 6 is broken, and thus, the electro-magnetic coil 6 becomes deenergized, turning on the electro-magnetic switch 8, as shown with a solid line in FIG. 11. Accordingly, the indicator lamp 9 is energized, prompting the user to replace the brake pad.
When the conventional pad wear indicator described above has worn by a preset amount, it suddenly prompts the user to replace the brake pad without much warning. Since the remaining amount in which the user is to be prompted to replace the brake pad is made the minimum value, he or she, upon being suddenly prompted to replace the brake, may lack sufficient time to do so. If the lamp goes on during running, he or she may panic or lose his or her peace of mind. While the setup remaining amount of the lining could be increased to avoid panic by allowing the car operator adequate time in which to replace the brake pad, premature indication of a worn brake pad is wasteful.